The present invention is directed to an auxiliary back-up and trailer coupling device for motor vehicles which employs ultrasonic sensors. The ultrasonic sensors are mounted on the motor vehicle, are capable of both transmitting and receiving, and are linked to a control unit and display device.
Providing motor vehicles with so-called collision-warning devices, which employ ultrasonic sensors to detect the distance to other objects in the immediate vicinity of the vehicle, is generally known. Such collision-warning devices are designed to emit warning signals when the distance between the vehicle and the objects falls below a predetermined minimum clearance.
Known collision-warning devices, which work according to the echo-sounding principle, are preferably mounted in the rear vehicle area and irradiate sound waves to the rear of the vehicle in an area that cannot be seen by the driver of the motor vehicle. However, such devices give the driver only very general information about whether an obstacle is situated in the rear area of the motor vehicle and what clearance this obstacle has from the motor vehicle.
Unfortunately, such known collision warning devices are inadequate in many situations. In particular, when a vehicle having a coupling is being backed-up to engage (i.e., hitch) a trailer, the only information provided by the known collision warning devices is that an obstacle is present. It would be desirable to have information about the exact position of the trailer's tow bar with respect to the coupling of the motor vehicle.
In particular, damage often occurs when trailers are being hitched to towing vehicles because the coupling of the motor vehicle often does not exactly meet with the trailer tow bar. Since the trailer tow bar is generally an eye ring or a ball head and has relatively small dimensions and reflects poorly, the known echo sounding method employing ultrasonic sensors is unsuitable.
Furthermore, the use of infrared sensors, in addition to the ultrasonic sensors, has been proposed. However, when these sensors are installed so as to be immovable, they disadvantageously cover only a relatively narrow range. As a result, they cannot locate with certainty the tow-bar head of a trailer, for example. Moreover, infrared emitters are very sensitive to pollution. This inhibits their ability to function properly, especially for use with trucks. In addition, infrared emitters have the undesired characteristic of reacting to the effects of outside light, rendering applications under strong insolation (e.g., exposure to sunlight) virtually impossible.
Thus, there exists a need for an auxiliary back-up and coupling device permitting objects situated in the rear area of a motor vehicle, and in particular in the head of a tow bar, to be reliably recognized and positioned. The device preferably employs only one sensor type and remains effective even under difficult environmental conditions.